NAME

SYNOPSIS

DESCRIPTION

[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C
standard.

The perror() function shall map the error number accessed through the symbol errno to a language-dependent error
message, which shall be written to the standard error stream as follows:

First (if s is not a null pointer and the character pointed to by s is not the null byte), the string pointed to
by s followed by a <colon> and a <space>.

Then an error message string followed by a <newline>.

The contents of the error message strings shall be the same as those returned by strerror() with argument errno.

[CX] The
perror() function shall mark for update the last data modification and last file status change timestamps of the file
associated with the standard error stream at some time between its successful completion and exit(), abort(), or the completion of fflush() or fclose() on stderr.

The perror() function shall not change the orientation of the standard error stream.

On error, perror() shall set the error indicator for the stream to which stderr points, and shall set errno
to indicate the error.

Since no value is returned, an application wishing to check for error situations should call clearerr(stderr)
before calling perror(), then if ferror(stderr) returns non-zero, the value of errno indicates which
error occurred.